I'm not a diesel owner and had no experience of DPF procedure before. However, the following vid gives some guidance. Indication of events to do with DPF appears to be the check engine light and what the code reader in the vid reveals.

I would have thought (hoped) your handbook would have explained procedure ..a bit?

Manual Regen is by Nissans own software tool normally. There are other expensive tools however of the make in this video.